1. Field of Invention
The invention relates to a control device for hybrid vehicles.
2. Description of Related Art
There exists a parallel hybrid system, in which both an engine and a motor/generator are attached to a transmission at the time of starting and acceleration. Drive forces from both the engine and the motor/generator are transmitted to the transmission. When a vehicle is running on a downward slope or subjected to braking, the motor/generator functions as a generator to compensate for an engine brake effect and to regenerate a braking energy to improve fuel consumption and reduce an emission of exhaust gases (see, for example, JP-A-9-215270).
Also, there exists a series hybrid system, in which an engine, a motor, and a generator are attached to a transmission. The engine drives the generator to generate electricity, by which the motor is driven for running, and the engine with a small output is operated quasi-steadily in an efficient region to cause a running of a vehicle while efficiently charging a battery with electricity (see, for example, JP-A-5-168105).
Being not limited to hybrid vehicles (Hybrid Electric Vehicle), in vehicles that run on a drive torque provided only by an engine, when a vehicle performs an inertial running (coast running) without relying on engine torque, a driver again steps on an accelerator pedal and an automatic transmission is provided between the engine and drive wheels, switchover to a driving state is made. Switchover to a driving state is made in which a quantity of engine torque produced by a corresponding start of the engine exceeds a quantity of torque transmitted through the transmission from a side of the drive wheels. Thereby, mutually meshing gears momentarily strike against one another to generate so-called crank noises.
In order to avoid such a disadvantage engine torque can be reduced by making use of an electronic controlled throttle, or a control for regulation of engine ignition timing with lag setting.